Google Closure Library

ClojureScript projects always auto-include the
Google Closure Library,
a massive library built and used by Google on many of their products
(Gmail, Docs, etc). It has low-level utilities for DOM manipulation,
server communication, animation, data structures, unit testing,
rich-text editing, and UI widgets/controls.

Try the wrapper libraries first!

You may first want to consider the following ClojureScript libraries
which wrap some functionality from Google Closure Library. Their source
code also serves as good examples of how to use Closure directly.